ABCD

Example

A
B
A
_
C
B
C
_
B
B
C
18
17
15
20
 
 
A
B
C
_
_
_

Solution

A
B
A
13
C
B
C
21
B
B
C
18
17
15
20
 
 
A
B
C
4
5
8
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ABCD
ABCD

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